Field of the Invention
The present invention relates to a solid state image sensor and a method for manufacturing the same.
Description of the Related Art
Japanese Patent Laid-open No. 2012-23319 discloses a manufacturing method aiming to uniformize the dark current that occurs in, of the effective pixel region of a solid state image sensor, a portion that is in the vicinity of the optical black pixel region and a central portion that is distant from the optical black pixel region. According to this method, the protective film is formed such that its portion located above the optical black pixel region has a greater thickness than its portion located above the effective pixel region. During sintering, at the portion of the effective pixel region in the vicinity of the optical black pixel region, some of the hydrogen supplied from the protective film to the substrate is absorbed into the light shielding layer of the optical black pixel region. At the portion of the effective pixel region in the vicinity of the optical black pixel region, the amount of hydrogen supplied from the protective film to the surface of the substrate is increased by forming the protective film such that its portion located above the optical black pixel region has a large thickness. This configuration uniformizes the amount of hydrogen supplied to the substrate surface at the portion in the vicinity of the optical black pixel region and the central portion distant from the optical black pixel region, of the effective pixel region. Consequently, this configuration reduces the variation of the dark current all over the effective pixel region.